The transmission of a tracked vehicle is typically much different than the transmission of a wheeled vehicle. This is due to the fact that a wheeled vehicle has the ability to rotate a single or plurality of wheels with respect to the vehicle longitudinal direction, so as to induce a yaw component to the direction of travel, resulting in a turn. A tracked vehicle can operate with the same logic, provided there are a plurality of tracks that can be independently rotated with respect to the vehicle longitudinal axis. However, most tracked vehicles only have two parallel tracks that are at a fixed angle to the vehicle longitudinal axis. Therefore, steering must be induced by independently varying the speed of the tracks.
Conventional schemes for independently varying track speed include using separate drives for each track, a combination of clutches and brakes, and differentials with hydrostatic bias. These schemes, however, ultimately impose a negative drag torque to the inner track while the vehicle is turning, which induces high loadings on the transmission components and thereby requires the use of oversized transmission components.